1. Field of the Invention
The invention relates to a control device for a marine gearbox and engine, and in particular to a device for use with a single lever control adapted to control concurrently an engine and reversible marine gearbox, and an override throttle control for use with the gearbox in neutral.
2. Prior Art
Single lever controls are widely used in marine applications, particularly in multi-station arrangements where the main propulsion engine and clutch and gearbox assembly can be controlled from several different locations or stations in the vessel through single lever control heads provided at the stations. The gearbox usually incorporates two clutches associated with forward and reverse gears and can be referred to as a clutch and gearbox assembly, or more simply as a gearbox. The lever has an intermediate neutral position straddled by forward and reverse positions in which the lever can move between idle and full speed in either forward or reverse. In many applications where auxiliary equipment, such as a pump or winch, is to be operated by the main propulsion engine, a separate independent throttle control is also provided to control the engine when powering the auxiliary apparatus alone and the main gearbox is in neutral. This separate control is referred to as an override throttle control and preferably an interlock is provided to prevent operation of the override throttle control except when the gearbox is in neutral.
it can be appreciated that these various control functions have to be integrated into a common input apparatus, and then split as two separate control functions which are coupled separately to the engine and gearbox. This apparatus can be referred to as a control function splitter apparatus which receives an input signal from one of the single lever control heads. This signal results initially in selecting either forward or reverse from the neutral position in the gearbox, after which the throttle can be shifted from idle to any position up to full throttle. It is important that the engine is not accelerated until the forward or reverse gear is fully engaged, and correspondingly it is important that the gear is not shifted until the engine has been returned to idle. Such splitter apparatus is usually positioned remotely from the various control heads and is connected to the controls through push-pull cables, pressurized fluid lines, tensioned cables and sheaves, etc. In larger vessels, where lengths of lines or cables and the number of stations can become excessive, pneumatic controls are preferable to push-pull cables or cable and sheave systems.
Commonly, prior art splitter apparatus coupling the various control heads to the engine and gearbox have been complex and have commonly resulted in a non-linear relationship between control lever setting and throttle position. This often resulted in a non-characteristic "feel" at the control lever in which an operator may experience difficulty in "feeling" selection of the particular mode of gearbox operation. Also, the non-lineality of the splitter apparatus sometimes introduced difficulties where the engine speed governor had sufficient force to cause "creep" in the controls, such that a desired engine setting is not maintained unless continually monitored and manually corrected as required.